The titrimetric analysis or titrimetry is a determination method of the chemical analytics, in which the dissolved substance to be determined (the titrant or solution to be titrated) is reacted with an other substance of known concentration (the titrans, titration liquid, standardized solution), also mostly in a dissolved state, up to an end point, equivalency point or apex point (called hereinafter “end point” in a summarizing manner). The determination procedure is called titration. The end point is indicated by an indicator system, for instance, or in an electrochemical way or by means of a precipitation reaction.
For measuring the standardized solution, the burette is conventionally used. Further known is a metering system which is applicable to titration purposes. The latter has a metering equipment realised as a hand-held instrument, into which a syringe for the pick-up and delivery of liquids is insertable. For the instrumentation of the metering equipment, there are syringes with different nominal volumes. The metering system is switchable into a titration mode, which is characterised in that the speed of the syringe plunger or the delivered mass flow is decreased automatically about one level at each delivery step, in order to make more precise titration possible. Finally, the speed remains constant at the lowermost level.
In the titration systems up to now, there is the danger that too much liquid can be delivered in the region of the end point upon unintended wrong procedure. Even when a small mass flow is delivered in the proximity of the end point with the known metering system, it may happen that the end point is missed. For instance, reaching the end point is recognised too late because titrant and titrans do not mix homogeneously and react with each other instantly. Furthermore, the user needs a reaction time from recognising the end point up to releasing the triggering button, during which further titrans flows in and the end point can be exceeded. When using the metering equipment with syringes having different nominal volumes, the delivered mass flows can be very different in a certain delivery step. Use of different syringes may also complicate the determination of the end point.
If the end point is missed in the context of a pH-value adjustment for an unbuffered or weakly buffered solution, the expense for correction may be very time-consuming. It is also possible that corrections lead to a dilution of the component(s) of interest in the solution to be processed, which is too high for the following working steps. In this case, the titrated solution has to be discarded. If the end point is exceeded in an analytic goal, the probable end point can be sometimes found by interpolation. When this is not possible or not allowed for procedural regulations, the titration has to be repeated with an additional sample.
Departing from this, the present invention is based on the objective to provide a system and method for titration which makes it possible to facilitate the recognition of the end point of the titration.